Choking is never pretty to watch, whether by a football team, in a child or by a political candidate suddenly running in blind panic. Nobody does the choke better than Hillary Clinton.

She famously choked in 2008, when her cakewalk to the Democratic presidential nomination was suddenly interrupted by Barack Obama, an upstart first-term senator from Illinois, an inexperienced radical, and black besides. Not exactly a candidate with all the conventional advantages. Hillary came through with an epic choke, and the rest is history.

Hillary’s very bad, not at all good week has put another cakewalk on hold. The polls are tightening dramatically, the FBI and WikiLeaks keep coming at her, and on the stump Hillary’s looking a hint unhinged. She’s beginning to shriek. She’s still the favorite, but no longer by very much, and her most faithful acolytes, from Wall Street to K Street to Hollywood Boulevard, are wetting their pants.

Patrick Caddell, a veteran of the polling trade for Democratic presidential candidates, says Hillary suddenly “looks kind of hysterical, out there making wild attacks now, and going crazy.”

She opened the last full week on the stump with a broadside that the Republican campaign enjoys the advantage of ties between Donald Trump and Vladimir Putin. She took this from idea from Slate, a beacon of misinformation (and sometimes disinformation) on the left, and this was soon too much even for The New York Times. The lighter-than-air charge blew away on the first breeze of the morning.

“I think they don’t know what to do do,” Mr. Caddell says, with Hillary’s negatives and unfavorables higher than the Donald’s deplorables. He turned on the television the next morning and “the hysteria on MSNBC was palpable.”

“This thing will move in its own direction,” he says, “but I think things could be coalescing. It’s not just the emails. It’s the larger attitudes about the country.”

Sometimes an observant man senses movement even before the polls do, but this time the hunch and the polls say the same thing, that something is going on out there in the strange and the dark in Peoria and beyond. Some observers liken it to the campaign of 1980, which Jimmy Carter led all the way to the final week, thinking he had successfully relegated the Gipper to the backwoods of Upper Oblivia by painting him as a wild man eager to get on with World War III.

Without even an October surprise, the worm and the tide turned, almost as if in tandem, and in the last seven days of the campaign the Gipper caught fire and won it going away. In another week it would have been a landslide.

Hillary remains the betting favorite, though the odds seem to be shrinking almost hourly. All the consultants’ predictive models say so. Nate Silver’s closely watched website FiveThirtyEight, accurate in the past, gives the Donald only a 30 percent chance of winning, but that’s twice the 15 percent chance as calculated for him on October 17.

Democrats, trying to keep their pants dry as they whistle past this graveyard, insist they’re still confident but concede that Hillary’s margin might be narrower than they once thought, and maybe the margin won’t be enough to win the four seats the Democrats must have to take back the Senate. (The House, everybody agrees, is no longer in peril.)

Robert Shrum, a senior strategist for several Democratic presidential candidates, still has his lunch money on Hillary, but concedes there “may be some” fallout from James Comey’s dramatic announcement that the FBI has resumed its investigation into Hillary’s email-and-national security debacle.

The Donald has even been closing the gap among women, though Hillary continues on the right side of the vast divide. What has put her campaign in panic mode is that the turnout of black voters looks to be down dramatically, despite the spirited campaigning of President Obama. Hillary is trying everything, even pretending to like turnip greens, cornbread and black-eyed peas in soul-food joints in Florida. “The blacks are just not listening,” one Democratic strategist says. “They don’t like Hillary any more than anyone else does.”

In the last days and hours of any campaign it’s movement and momentum — what George Bush the Elder called “the big mo” — that counts most. Once momentum gathers speed it pushes aside everything, and there’s not much anyone can do to stop it. If such a wave appears, it will have to appear soon.

Everybody searches for a metaphor to explain the unknown. “The days right before an election are like the re-entry of a spacecraft,” says Bob Shrum. ” We just don’t know what’s going to happen.” And that, dear heart, is what’s so scary.